Abstract

We present the design, implementation and validation of a swept-source optical coherence tomography (OCT) system for real-time imaging of the human middle ear in live patients. Our system consists of a highly phase-stable Vernier-tuned distributed Bragg-reflector laser along with a real-time processing engine implemented on a graphics processing unit. We use the system to demonstrate, for the first time in live subjects, real-time Doppler measurements of middle ear vibration in response to sound, video rate 2D B-mode imaging of the middle ear and 3D volumetric B-mode imaging. All measurements were performed non-invasively through the intact tympanic membrane demonstrating that the technology is readily translatable to the clinic.

Conceptual diagram describing the memory and grid structure of the CUDA streams used for A) pre- and B) post-DFT processing the raw unstitched interferometric data. DVV: data valid vector describing the pattern of invalid data to be ignored in the spectral interferograms, NORM: complex normalization vector used for application of ripple-rejection, dispersion compensation and windowing prior to discrete Fourier-transformation.

A) Optical layout B) Closeup of the middle ear OCT scanning microscope used for imaging down the ear canal through a 4 mm otoscopic speculum and mounted to surgical microscope arm. C) Complete in-clinic, real-time imaging system mounted to an articulating arm. Units are in mm.

Ex vivo, Doppler-vibrographic response of a cadaveric right ear at an acoustic frequency of 515Hz showing a 2D view of the ear’s measured peak-to-peak vibrational response A) without acoustic stimulus, and B) with stimulus applied at 100dBSPL. C) and D) show the color-mapped vibrational response to stimulus in 3D before and after digital removal of the TM (see Visualization 1). Visualization 2 uses the same data to animate the middle ear’s vibrational response. Tympanic membrane (TM), malleus (M), incus (IN), cochlear promontory (CP).

In vivo, real-time functional imaging of a normal left ear’s response at 1030Hz. A) Shows a 1 × 1cm2 2D cross-section of the middle ear in the transverse plane. Visualization 3 shows the macroscopic changes to the ear anatomy during a Valsalva maneuver. B) Shows a 1 × 1 × 1cm3 3D volume render of the middle ear as seen from the perspective of the ear canal with the TM digitally removed (see Visualization 4), and C) from an inferior-posterior perspective with the TM in-place showing the axis of Doppler measurement along the yellow line passing through the incus at the stapedius tendon. Functional measurements of the TM and incus’ peak-to-peak vibrational response at 1kHz are shown in D) with a 100dBSPL tone applied to the ear and E) without stimulus. F) A plot of displacement response versus sound pressure level showing excellent linearity from 80dBSPL to 100dBSPL. Error bars represent ± one standard deviation of the response over the pixels along the axial length of the incus. Tympanic membrane (TM), malleus (M), incus (IN), incudo-stapedial joint (IS), stapedius tendon (ST), chorda tympani nerve (CT), cochlear promontory (CP), round-window niche (RW).